POROUS POLYPROPYLENE FILM AND PROCESS FOR MANUFACTURING SAME

摘要

The present invention pertains to: a porous polypropylene film which comprises a polypropylene resin and has a deviation of film-widthwise 3% shrink temperature of less than 0.05 as represented by formula (1); and a process for manufacturing the same. The porous polypropylene film exhibits extremely excellent uniformity of film-widthwise thermal dimensional change. Deviation of film-widthwise 3% shrink temperature = (Tmax - Tmin)/Tave ··· (1) [wherein Tmax is the highest of the temperatures at measuring points which are present on the film-widthwise shrink curve and at which 3% shrink is observed; Tmin is the lowest of the temperatures at measuring points which are present on the film-widthwise shrink curve and at which 3% shrink is observed; Tave is the average of the temperatures at all measuring points present on the film-widthwise shrink curve; and measuring points present on the film-widthwise shrink curve are the center in the width direction of the film and positions located at intervals of 30mm from the center toward both edges]